System, method, and computer-readable medium for user equipment handoff from a macrocellular network to an IP-femtocell network

ABSTRACT

A system, method, and computer readable medium for handoff of a user equipment from a macrocellular system to a femtocell system is provided. A micro-pilot assisted handoff routine may be implemented to facilitate handoff of a user equipment from a macrocellular system to a femtocell system. The femtocell system may transmit very low power pilot, paging, and synch channels on a common frequency used by the macrocellular system. In another embodiment, a mobile assisted handoff routine facilitates handoff of a user equipment from a macrocellular system to a femtocell system. The user equipment&#39;s preferred roaming list includes an entry for the femtocell system and specifies a SID/NID and pseudo-noise offset for the femtocell system. The user equipment is configured to periodically enter a search mode to attempt to locate the femtocell system by switching to a femto carrier that is specified in the preferred roaming list.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional patent applicationSer. No. 60/936,626 entitled FEMTOCELL filed Jun. 21, 2007, and claimspriority to U.S. provisional patent application Ser. No. 61/003,151entitled SIP-IOS ADAPTER FUNCTION filed Nov. 15, 2007, the disclosure ofeach of which is incorporated in its entirety herein by reference.

FIELD OF THE INVENTION

The present invention is generally related to radio access technologiesand, more particularly, to mechanisms for transfer of a user equipmentfrom a macrocellular network to a femtocell network.

BACKGROUND OF THE INVENTION

Contemporary cellular radio systems, or mobile telecommunicationsystems, provide an over-the-air interface to wireless user equipments(UEs) via a radio access network (RAN) that interfaces with at least onecore network. The RAN may be implemented as, for example, a CDMA2000RAN, a Universal Mobile Telecommunications System (UMTS) RAN, a GlobalSystem for Mobile communications (GSM) RAN, or another suitable radioaccess network implementation. A UE may comprise, for example, a mobileterminal such as a mobile telephone, a laptop computer featuring mobiletelephony software and hardware, a personal digital assistant (PDA), orother suitable equipment adapted to transfer and receive voice or datacommunications with the radio access network.

A RAN covers a geographical area comprised of any number of cells eachcomprising a relatively small geographic area of radio coverage. Eachcell is provisioned by a cell site that includes a radio tower, e.g., abase transceiver station (BTS), and associated equipment. BTSscommunicate with UEs over an air interface within radio range of theBTSs.

Numerous BTSs in the RAN may be communicatively coupled to a basestation controller, also commonly referred to as a radio networkcontroller (RNC). The BSC manages and monitors various system activitiesof the BTSs serviced thereby. BSCs are coupled with at least one corenetwork.

BTSs are typically deployed by a carrier network in areas having a highpopulation density. The traffic capacity of a cell site is limited bythe site's capacity and affects the spacing of cell sites. In suburbanareas, sites are often up to two miles apart, while cell sites deployedin dense urban areas may be as close as one-quarter of a mile apart.Because the traffic capacity of a cell site is finitely limited, as isthe available frequency spectrum, mobile operators have a vestedinterest in technologies that allow for increased subscriber capacity.

A microcell site comprises a cell in a mobile phone network that coversa limited geographic area, such as a shopping center, hotel, airport, orother infrastructure that may have a high density mobile phone usage. Amicrocell typically uses power control to limit the radius of themicrocell coverage. Typically a microcell is less than a mile wide.

Although microcells are effective for adding network capacity in areaswith high mobile telephone usage, microcells extensively rely on theRAN, e.g., a controlling BSC and other carrier functions. Becausecontemporary BSCs have limited processing and interface capacity, thenumber of BTSs—whether microcell BTSs or typical carrier BTSs—able to besupported by the BSC or other RAN functions is disadvantageouslylimited.

Contemporary interest exists in providing enterprise and office access,including small office/home office (SOHO) radio access, by an evensmaller scale BTS. The radio coverage area of such a system is typicallyreferred to as a femtocell. In a system featuring a femtocell, a UE maybe authorized to operate in the femtocell when proximate the femtocellsystem, e.g., while the UE is located in the SOHO. When the UE movesbeyond the coverage area of the femtocell, the UE may then be servicedby the carrier network. The advantages of deployment of femtocells arenumerous. For instance, mobile users frequently spend large amounts oftime located at, for example, home, and many such users rely extensivelyon cellular network service for telecommunication services during thesetimes. For example, a recent survey indicated that nearly thirteenpercent of U.S. cell phone customers do not have a landline telephoneand rely solely on cell phones for receiving telephone service. From acarrier perspective, it would be advantageous to have telephone servicesprovisioned over a femtocell system, e.g., deployed in the user's home,to thereby reduce the load, and effectively increase the capacity, onthe carrier RAN infrastructure. However, various issues related tohandoff of communication services from a macrocellular system to afemtocellular system remain unresolved.

Therefore, what is needed is a mechanism that overcomes the describedproblems and limitations.

SUMMARY OF THE INVENTION

The present invention provides a system, method, and computer readablemedium for handoff of communication services from a macrocellular systemto a femtocell system. In one implementation, a micro-pilot assistedhandoff routine may be implemented to facilitate handoff of a userequipment from a macrocellular system to a femtocell system. In thisembodiment, a femtocell system or an adjunct thereto may transmit verylow power pilot, paging, and synch (PPS) channels on a common frequencyused by the macrocellular system. In a particular implementation, themacrocellular system, femtocell system, and pilot may all be commonlytransmitted on a common carrier, F1, in a single-carrier system sincethe macrocellular system, femtocell system, and pilot are protected byPN orthogonality. In other implementations, the pilot may be on a firstcarrier, F1, and the femtocell system may be on a second carrier, F2.The PPS may include a unique SID/NID assigned to the femtocell system.In other implementations, another unique identifier may be assigned tothe femtocell system in lieu of a SID/NID, and reference to a SID/NIDassigned to a femtocell system is exemplary only. Detection of the PPSat a pseudo-noise (PN) allocated for the femtocell system provides anindication that the user equipment is within range of a femtocellsystem. The user equipment may then compare the SID/NID with a SID/NIDincluded in the user equipment's preferred roaming list to determine ifthe user equipment is authorized to access the femtocell system. If so,the user equipment may then attempt to register with the femtocellsystem. In another embodiment, a mobile assisted handoff routinefacilitates handoff of a UE from a macrocellular system to a femtocellsystem. Handoff of the UE from a macrocellular system to a femtocellsystem may be made as an active handoff, i.e., handoff of the UE that isengaged in an active call, or an idle handoff, i.e., switching of the UEfrom a macrocellular system to a femtocell system when the UE is notactively engaged in a call. In this implementation, the user equipment'spreferred roaming list (PRL) may be provisioned either manually orover-the-air. A PRL entry for the femtocell system may include a uniqueSID/NID and pseudo-noise offset for one or more femtocell systems withwhich the user equipment is authorized to access. The user equipment maybe configured to periodically enter a search mode to attempt to locatethe femtocell system by switching to a femto carrier that is specifiedin a preferred roaming list entry allocated for the femtocell system andlook for the femtocell pseudo-noise offset specified in the preferredroaming list entry. If the pseudo-noise offset is located, the UE maythen decode the SID/NID and determine whether the SID/NID matches theSID/NID of the home femtocell system. If the SID/NID matches, the userequipment may then register on the femtocell system.

In one embodiment of the disclosure, a method for handoff of a userequipment from a macrocellular system to a femtocell system is provided.The method includes provisioning the user equipment with a preferredroaming list that includes an entry allocated for the femtocell systemthat specifies a system identification number and network identificationnumber associated with the femtocell system, detecting, by the userequipment, a system identification number and network identificationnumber over an air interface, and evaluating the preferred roaming listto determine whether the detected system identification number andnetwork identification number match the system identification number andthe network identification number associated with the femtocell system.

In another embodiment of the disclosure, a computer-readable mediumhaving computer-executable instructions for execution by a processingsystem, the computer-executable instructions for facilitating handoff ofa user equipment from a macrocellular system to a femtocell system isprovided. The computer-readable medium includes instructions forprovisioning the user equipment with a preferred roaming list thatincludes an entry allocated for the femtocell system that specifies asystem identification number and network identification numberassociated with the femtocell system, reading a pseudo-noise offsetassociated with the femtocell system from the preferred roaming list,detecting, by the user equipment, a system identification number andnetwork identification number over an air interface at the pseudo-noiseoffset, and evaluating the preferred roaming list to determine whetherthe detected system identification number and network identificationnumber match the system identification number and the networkidentification number associated with the femtocell system.

In a further embodiment of the disclosure, a system configured formacrocellular to femtocell system handoff is provided. The systemincludes a packet-switched network, an Internet Protocol multimediasubsystem communicatively interfaced with the packet-switched network, amacrocellular system with which a user equipment has authorized access,and a femtocell system communicatively coupled with the packet-switchednetwork that is adapted to provide a radio interface with the userequipment. The femtocell system is configured with an electronic serialnumber of the user equipment, and the user equipment is provisioned witha preferred roaming list that includes an entry allocated for thefemtocell system that specifies a system identification number andnetwork identification number associated with the femtocell system. Thefemtocell system transmits a system identification number and networkidentification number that is detected by the user equipment. The userequipment evaluates the preferred roaming list to determine whether thedetected system identification number and network identification numbermatch the system identification number and the network identificationnumber associated with the femtocell system.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures, in which:

FIG. 1 is a diagrammatic representation of a network system thatincludes a cellular network adapted to provide macro-cellular coverage;

FIG. 2 is a diagrammatic representation of a conventional network systemconfiguration featuring a femtocell;

FIG. 3 is a diagrammatic representation of a network system in which afemtocell system implemented in accordance with an embodiment of thepresent invention may be deployed;

FIG. 4A is a simplified diagrammatic representation of the femtocellsystem depicted in FIG. 3 that may be connected with an IP backhaul inaccordance with an embodiment;

FIG. 4B is a simplified diagrammatic representation of an alternativeembodiment of a femtocell system that may be connected with an IPbackhaul;

FIG. 5 is a diagrammatic representation of an exemplary sessioninitiation protocol registration message generated by a femtocell systemon behalf of a user equipment in accordance with an embodiment;

FIG. 6 is a diagrammatic representation of a network system featuring afemtocell network implemented in accordance with an embodiment;

FIG. 7 is a diagrammatic representation of an exemplary softwareconfiguration of a user equipment adapted for engaging in communicationswith femtocell systems in accordance with an embodiment;

FIG. 8 is a flowchart depicting a micro-pilot assisted handoff routinethat facilitates handoff of a user equipment from a macrocellularnetwork to a femtocell system in accordance with an embodiment; and

FIG. 9 is a flowchart depicting a mobile assisted handoff routine thatfacilitates handoff of a user equipment from a macrocellular network toa femtocell system in accordance with an alternative embodiment.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the following disclosure provides manydifferent embodiments or examples for implementing different features ofvarious embodiments. Specific examples of components and arrangementsare described below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting.

FIG. 1 is a diagrammatic representation of a network system 100 thatincludes a cellular network 110 adapted to provide macro-cellularcoverage to a user equipment. Cellular network 110 may comprise, forexample, a code-division multiple access (CDMA) network, such as aCDMA-2000 network.

Cellular network 110 may include any number of base transceiver stations(BTSs) 112 a-112 c communicatively coupled with a base stationcontroller (BSC) 114 or RNC. Each individual BTS 112 a-112 c under thecontrol of a given BSC may define a radio cell operating on a set ofradio channels thereby providing service to a user equipment (UE) 125,such as a mobile terminal. BSC 114 manages the allocation of radiochannels, receives measurements from mobile terminals, controlshandovers, as well as various other functions as is understood. BSC 114is interconnected with a mobile services switching center (MSC) 116 thatprovides mobile terminal exchange services. BSC 114 may be additionallycoupled with a packet data serving node (PDSN) 118 or other gatewayservice that provides a connection point between the CDMA radio accessnetwork and a packet network, such as Internet 160, and providesmobility management functions and packet routing services. MSC 116 maycommunicatively interface with a circuit switched network, such as thepublic switched telephone network (PSTN) 150, and may additionally becommunicatively coupled with an interworking function (IWF) 122 thatprovides an interface between cellular network 110 and PSTN 150.

System 100 may also include a signaling system, such as a signalingsystem #7 (SS7) network 170. SS7 network 170 provides a set of telephonysignaling protocols which are used to set up the vast majority of theworld's PSTN telephone calls. SS7 network 170 is also used in cellularnetworks for circuit switched voice and packet-switched dataapplications. As is understood, SS7 network 170 includes varioussignaling nodes, such as any number of service control points (SCPs)172, signal transfer points (STPs) 174, and service switching points(SSPs) 176.

BTSs 112 a-112 c deployed in cellular network 110 may service numerousnetwork 110 subscribers. Cell cites provided by BTSs 112 a-112 ccommonly feature site ranges of a quarter to a half mile, e.g., indensely populated urban areas, to one to two miles in suburban areas. Inother remotely populated regions with suitable geography, site rangesmay span tens of miles and may be effectively limited in size by thelimited transmission distance of relatively low-powered UES. As referredto herein, a cell provided by a BTS deployed in carrier network 110 foraccess by any authorized network 110 subscriber is referred to as amacrocell.

FIG. 2 is a diagrammatic representation of a conventional network system200 configuration featuring a femtocell. In the depicted example, acentral BSC 214 deployed in a cellular carrier network 210 may connectwith a soft switch core 212 that is connected with a MSC 216. MSC 216connects with the cellular core network and may interface with othernetworks, such as the PSTN as is understood. BSC 214 may be connectedwith and service numerous BTSs 212 a-212 c that provide macrocells tocellular network 210 subscribers.

BSC 214 may additionally connect with a tunnel gateway system 218 thatis adapted to establish secured tunnels 232 a-232 x with respectivefemtocell systems 250 a-250 x. Femtocells comprise cellular accesspoints that connect to a mobile operator's network using, for example, aresidential DSL or cable broadband connection. Femtocells 250 a-250 xprovide a radio access point for UE 225 when the UE is within range of afemtocell system with which the UE has authorized access. For example,femtocell system 250 a may be deployed in a residence of the user of UE225. Accordingly, when the user is within the residence, mobiletelecommunications may be provided to UE 225 via an air-interfaceprovided by femtocell system 250 a. In this instance, UE 225 iseffectively offloaded from the macro BTS, e.g., BTS 212 a, andcommunications to and from the UE are carried out with femtocell system250 a over Internet 260. Thus, femtocell systems 250 a-250 x may reducethe radio resource demands by offloading UEs from macrocells tofemtocells and thereby provide for increased subscriber capacity ofcellular network 210.

In contemporary implementations such as that depicted in FIG. 2, afemtocell system 250 a comprises a transceiver without intelligence andis thus required to be connected and managed by BSC 214. Thus, femtocellsystems 250 a-250 x are reliant on the carrier network centralized BSC214 which has limited capacity and thus does not exhibit desirablescaling characteristics or capabilities. Moreover, high communicationsoverhead are realized by the BTS backhaul.

FIG. 3 is a diagrammatic representation of a network system 300 in whicha femtocell system implemented in accordance with an embodiment of theinvention may be deployed. System 300 includes a radio access network(RAN) 310 that provides an over-the-air interface with a UE 325, e.g., amobile terminal. RAN 310 may comprise, for example, a CDMA radio accessnetwork or another suitable RAN. RAN 310 may comprise various BTSs andassociated base station controllers BSCs as well as other infrastructureas is understood. UE 325 may be implemented as a personal digitalassistant (PDA), a mobile phone, a computer, or another device adaptedto interface with RAN 310.

System 300 may include an IP Multimedia Subsystem (IMS) 320 architectureadapted to provide IP service to UE 325. To this end, RAN 310 iscommunicatively coupled with a serving general packet radio service(GPRS) support node (SGSN) 314 and a gateway GPRS support node (GGSN)316. SGSN 314 provides the delivery of data packets from and to UE 325within its service area. GGSN 316 provides an interface between the GPRSbackbone network and external packet data networks. GGSN 316 iscommunicatively coupled with a policy decision function (PDF) 318 thatprovides authorization of media plane resources, e.g., quality ofservice (QoS) authorizations, policy control, bandwidth management, andthe like. PDF 318 may be communicatively coupled with a call sessioncontrol function (CSCF) 320.

CSCF 320 comprises various session initiation protocol (SIP) servers orproxies that process SIP signaling packets in IMS 320. CSCF 320 mayinclude a proxy-CSCF (P-CSCF) that provides a first point of contact foran IMS-compliant UE. The P-CSCF may be located in the visited network,or in the UE's home network if the visited network is not fullyIMS-compliant. UE 325 may discover the P-CSCF, e.g., by using DynamicHost Configuration Protocol (DHCP), or by assignment in a packet dataprotocol (PDP) context. CSCF 320 additionally includes a Serving-CSCF(S-CSCF) that comprises the central node of the signaling plane. TheS-CSCF comprises a SIP server, but additionally performs sessioncontrol. The S-CSCF is located in the home network and interfaces with ahome subscriber server (HSS) 340 to download and upload user profiles.CSCF 320 further includes an Interrogating-CSCF (I-CSCF) that comprisesa SIP function located at the edge of an administrative domain. TheI-CSCF has an IP address that is published in the Domain Name System(DNS) 372 that facilitates location of the I-CSCF by remote servers.Thus, the I-CSCF is used as a forwarding point for receipt of SIPpackets within the domain.

HSS 340 comprises a user database that supports the IMS network entitiesthat manage calls. HSS 340 stores user profiles that specifysubscription-related information of authorized users, authenticates andauthorizes users, and provides information about the user's physicallocation. Various application servers (AS) 342 a-342 n that host andexecute services interface with CSCF 320 via SIP.

CSCF 320 is coupled with a breakout gateway control function (BGCF) 322that comprises a SIP server that provides routing functionality based ontelephone numbers. BGCF 322 is used when a UE places a call from the IMSto a phone in a circuit switched network, e.g., PSTN 330, or the publicland mobile network. A media gateway controller Function (MGCF) 324performs call control protocol conversion between SIP and ISDN User Part(ISUP) and interfaces with a signaling gateway (SGW) 326. SGW 326interfaces with the signaling plane of a circuit switched network, e.g.,PSTN 330. SGW 326 may transform lower layer protocols, such as StreamControl Transmission Protocol (SCTP), into the Message Transfer Part(MTP) protocol, and pass ISUP data from MGCF 324 to PSTN 330 or anothercircuit switched network. A media gateway (MGW) 328 interfaces with themedia plane of PSTN 330 or another circuit switched network byconverting data between real-time transport protocol (RTP) and pulsecode modulation (PCM), and may also be employed for transcoding when thecodecs of the IMS and circuit switched networks differ. Resources of MGW328 are controlled by MGCF 324. Fixed access, e.g., IP telephony devices374 a-374 b, may connect with IMS network via Internet 370 that iscommunicatively coupled with IMS network 320 by way of border gateway360.

As is understood, DNS 372 comprises a scalable namespace thatfacilitates access to entities deployed on the Internet or privatenetworks. DNS 372 maintains various records for host names, servers, andthe like. For example, DNS 372 maintains records (commonly referred toas “A records”) that map hostnames to IP addresses, pointer (PTR)records that map IP addresses to canonical names to facilitate reverseDNS lookups, service (SRV) records that specify information on availableservices, naming authority pointer (NAPTR) records that facilitateregular expression based rewriting, and various other records. DNS 372may additionally include a telephone number mapping (ENUM) system thatfacilitates resolution of SIP addresses from E.164 number as isunderstood.

A base station manager (BSM) 378 may be deployed in Internet 370 and maybe adapted to communicate with numerous femtocell systems and femtocellnetworks. BSM 378 may provide various operations, maintenance, andmanagement functions to femtocell systems. For example, BSM 378 mayprovide service provisioning of femtocell systems, e.g., by providingconfiguration downloads to femtocell systems and preloading defaultconfiguration data for femtocell systems distributed via sales channels.BSM 378 may provide various support and maintenance features, such asalarm and periodic statistics reporting, automatic remote software imagedistribution to femtocell system, provide upgrades and reconfigurations,and may provide remote access via Internet 370 for diagnostics andcustomer support.

In accordance with an embodiment, a femtocell system 350 may includeintegrated BTS and BSC functions and may feature additional capabilitiesavailable in the provided femtocell site coverage area. Femtocell system350 provides an IP-accessible radio access network, is adapted foroperation with IMS 320, and provides radio link control functions.Femtocell system 350 may be communicatively coupled with Internet 370via any variety of backhaul technologies, such as an 802.11x link, a10/100 BaseT LAN link, a T1/E1 Span or fiber, cable set top box, DSLmodem connected with a central office digital subscriber line accessmultiplexer, a very small aperture terminal (VSAT), or another suitablebackhaul infrastructure.

In an embodiment, femtocell system 350 includes a session initiationprotocol (SIP) adapter that supports a SIP client pool and providesconversion of call set-up functions to SIP client set-up functions. Forexample, a SIP client pool allocated by femtocell system 350 maycomprise a plurality of SIP user agents 352 a-352 c that each may beallocated for a UE authorized to access femtocell system 350.Additionally, femtocell system 350 includes electronic serial number(ESN) screening, and/or Mobile Equipment Identifier (MEID) screening, toallow only designated UEs to access the femtocell thereby restrictingaccess to authorized home or small office UEs. For example, femtocellsystem 350 may be configured with an ESN list and/or MEID 354 thatspecifies ESNs and/or MEIDs of UEs authorized to access femtocell system350. In the illustrative example, ESNs of “ESN 1”-“ESN 3” are includedin ESN list 354. Provisioning of ESN(s) and/or MEID(s) may be made aspart of an initial femtocell system 350 activation. In the illustrativeexample, femtocell system 350 is allocated an Internet Protocol (IP)address of “66.249.73.42”, and UE 325 is allocated a mobile servicesISDN (MSISDN) number, or E.164 number, of “12145551212”.

FIG. 4A is a simplified diagrammatic representation of femtocell system350 depicted in FIG. 3 that facilitates provisioning of a femto-RAN inaccordance with an embodiment. Femtocell system 350 includes an antenna400 coupled with a BTS 410. BTS 410 may be implemented, for example, asa 1xRTT ASIC device and may comprise a non-diversity receiver featuringa built-in duplexer. In an embodiment, BTS 410 may feature only oneoperational band and may include a transmitter scan receiver and localoscillator. BTS 410 may be communicatively coupled with a BSC 420 thatprovides radio control functions, such as receiving measurements fromUEs, such as mobile phones, control of handovers to and from otherfemtocell systems, and may additionally facilitate handoff to or frommacrocells.

Femtocell system 350 includes an electronic serial number screeningfunction 430 that may facilitate approving or rejecting service for a UEby femtocell system 350. Additionally femtocell system 350 includes anInternet Operating System (IOS) and SIP Adapter (collectively referredto as IOS-SIP Adapter 440). IOS-SIP adapter 440 may invoke and manageSIP clients, such as a user agent (UA) pool comprising one or more UAs.In accordance with an embodiment, each UE 325 authorized to be servicedby femtocell system 350 may have a UA allocated therefor by femtocellsystem in a manner that facilitates transmission of communications toand from a UE over an IP backhaul. Accordingly, when an authorized UE iswithin the femtocell system 350 site range, telecommunication servicesmay be provided to the UE via the IP backhaul and femtocell system 350provisioned RAN. When the UE is moved beyond the service range offemtocell system 350, telecommunication service may then be provided tothe UE via macrocellular coverage.

To facilitate routing of calls from circuit switched call originators,femtocell system 350 may perform a DNS/ENUM registration on behalf ofUEs authorized to obtain service from femtocell system 350. In thepresent example, assume UE 325 with a MSISDN of “12145551212” has a SIPservice subscription in the domain “example.com” and has a SIP uniformresource identifier (URI) of “12145551212@example.com”. An exampleDNS/ENUM registration message generated by femtocell system 350 onbehalf of UE 325 and transmitted to DNS 372 is as follows:

$ORIGIN 2.1.2.1.5.5.5.4.1.2.1.e164.arpa. IN NAPTR 100 10 “u” “E2U+sip”“!{circumflex over ( )}.*$!sip:12145551212@example.com!”.

As is understood, the first line of the registration message comprisesthe MSISDN number of the UE converted (i.e., reversed with each numeraldelineated with a “.” character and appended with the e164.arpa domain)for DNS lookup. The second line of the registration message specifiesthe NAPTR record for the hosts that can further process the address—thedomain “example.com” (in which the UE with a URI of12145551212@example.com is registered) in the present example.

Femtocell system 350 may generate and issue a SIP registration on behalfof UE 325 authorized for service access by femtocell system 350.

FIG. 4B is a simplified diagrammatic representation of an alternativefemtocell system 450 that facilitates provisioning of a femto-RAN inaccordance with an alternative embodiment. Femtocell system 450 includesan antenna 400 coupled with a radio node (RN) 411. RN 411 may beimplemented, for example, as a 1xEV-DO ASIC device. For example, RN 411may provide a 1xEV-DO Rev. 0 air interface or a 1xEV-DO Rev. A airinterface. RN 411 may be communicatively coupled with a radio networkcontroller (RNC) 421 that provides radio control functions, such asreceiving measurements from UEs, control of handovers to and from otherfemtocell systems, and may additionally facilitate handoff to or frommacrocells. RNC 421 may also provide encryption/decryption functions,power, load, and admission control, packet scheduling, and various otherservices.

Femtocell system 450 includes an electronic serial number screeningfunction 430 that may facilitate approving or rejecting service for a UEby femtocell system 450. Additionally, femtocell system 450 includes anInternet Operating System (IOS) and SIP Adapter (collectively referredto as IOS-SIP Adapter 440). IOS-SIP adapter 440 may invoke and manageSIP clients, such as a user agent (UA) pool comprising one or more UAs.Each UE 325 authorized to be serviced by femtocell system 450 may have aUA allocated therefor by femtocell system 450 in a manner thatfacilitates transmission of communications to and from a UE over an IPbackhaul. Accordingly, when an authorized UE is within the femtocellsystem 450 site range, telecommunication services may be provided to theUE via the IP backhaul and femtocell system 450 provisioned RAN. Whenthe UE is moved beyond the service range of femtocell system 450,telecommunication service may then be provided to the UE viamacrocellular coverage. Femtocell system 450 may perform a DNS/ENUMregistration on behalf of UEs authorized to obtain service fromfemtocell system 450 and may generate and issue a SIP registration onbehalf of a UE authorized for service access by the femtocell system 450in a manner similar to that described above with reference to femtocellsystem 350.

FIG. 5 is a diagrammatic representation of an exemplary SIP registrationmessage 500 generated by femtocell system 350 on behalf of UE 325authorized for service access thereby in accordance with an embodiment.Registration message 500 may be transmitted from femtocell system 350 toa location service, such as a SIP registrar implemented as SIP Registrar380. Registrar 380 may provide the location and contact information tolocation service 382. Registration message 500 includes a REGISTER field510 that specifies the registration is being made within the domain“example.com”. In accordance with an embodiment, multiple contacts areincluded in registration message 500. In the present example,registration message 500 includes a contact field 512 that specifies aSIP contact for UE 325. Notably, the SIP contact field 512 for UE 325specifies the UA registered on behalf of UE with the URI12145551212@exmaple.com is located at the IP address of “66.249.73.42”.That is, the SIP contact registered by femtocell system 350 on behalf ofUE 325 is to be addressed at the femtocell system 350 address of66.249.73.42 thereby resulting in routing of SIP signaling messages tofemtocell system 325. In turn, femtocell system 350 may convert SIP callset up messaging to RAN signaling, allocate an uplink and a downlinkchannel for UE 325, and set up a call or data session thereon.

In the present example, registration message 500 includes a secondcontact field 514 that specifies a telephone URI, e.g., the MSISDN+1-214-555-1212 of UE 325. Thus, a location query for the SIP URIsip:12145551212@example.com would return two contacts. The first is theSIP URI that can be used to reach femtocell system 350, and thus UE 325thereby, and the second is the telephone URI that can be used to reachUE 325 via macrocellular coverage, i.e., via RAN 310. As is understood,the order of contacts 512-514 provides a contact preference, and themultiple contacts may be registered in separate registration messages.The depicted registration message including both the SIP contact URI andtelephone URI is exemplary only. Accordingly, in the present example, anattempt to contact UE 325 may first be made via the SIP URI12145551212@example.com. In the event that the session is notsuccessfully set up via the SIP contact, an attempt may be made to setupa session via RAN 310 using the telephone URI.

When the UE 325 moves outside the coverage area of femtocell system 350,another registration may be generated and submitted by femtocell system350 on behalf of UE 325 where the telephone URI is designated as thepreferred contact. Further, the SIP URI may be removed from theregistration when the UE 325 moves outside the coverage area offemtocell system 350 thereby avoiding any attempts to establish asession with UE 325 via femtocell system 350 when UE 325 has movedbeyond the femtocell system 350 coverage area.

To better facilitate an understanding of disclosed embodiments, considera call placed at circuit switched telephone 332 to UE 325. A gatewayreceives the call setup request, e.g., an Initial Address Message (IAM),and a query may be made with DNS 372 from which the domain “example.com”is resolved from the ENUM function. An INVITE message is thentransmitted to the example.com domain which, in turn, resolves thelocation of the called UE 325. Particularly, CSCF 320 may interrogatelocation server 382 and determine UE 325 is registered as located at theIP address 66.249.73.42. Accordingly, the INVITE message is routed toproxy server 376 which forwards the INVITE message to femtocell system350. Femtocell system 350 may then perform paging, channel allocation,and other procedures for provisioning a radio interface with UE 325 andissue SIP responses on behalf of UE 325. Thus, from a networkperspective, femtocell system 350 appears as a user agent to which thecall is directed. Further, UE 325 does not require a SIP client forreceiving the call because femtocell system 350 advantageously performssignaling and media conversion for signaling and media transmissionsover-the-air interface with 325. Thus, femtocell system 350 may appearas a conventional BTS to UE 325. A call from UE 325 to another terminal,such as circuit-switched telephone 332, a SIP client such aspacket-switched telephony device 374 a, or another device, may similarlybe facilitated by femtocell system 350.

As a second example, assume UE 325 has moved beyond the range offemtocell system 350. As noted above, femtocell system 350 may generateand transmit a registration message that excludes the SIP contact tofacilitate provisioning of telecommunication services via macrocellcoverage, e.g., via RAN 310. For instance, femtocell system 350 mayperiodically perform power measurements with UE 325, and upon the powermeasurement dropping below a particular power threshold, femtocellsystem may determine UE 325 is to be serviced by macrocellular coverage.Alternatively, a user may select macrocellular coverage via a userinterface provided on UE 325. In this instance, UE 325 may provide anindication to femtocell system 350 that telecommunication services areto be provided by RAN 310. Other scenarios may similarly result in adetermination that UE 325 is to be serviced by RAN 310. Upon such adetermination, femtocell system 350 may generate and transmit aregistration message on behalf of UE 325 to a registrar service, e.g.,CSCF 320 and SIP registrar 380. The contact information may then beupdated in location server 382 to indicate the telephone URI as thecontact of UE 325. In this scenario, consider a call placed at circuitswitched telephone 332 to UE 325. A gateway receives the call setuprequest, e.g., an Initial Address Message (IAM), and a query may be madewith DNS server 372 from which the domain “example.com” is resolved fromthe ENUM service. An INVITE message is then transmitted to theexample.com domain which resolves the location of called UE 325. In thepresent example, CSCF 320 may interrogate location server 382 anddetermine UE 325 has a preferred contact registered as a telephone URIof 2145551212. Accordingly, the INVITE message is routed to a gatewayserver, e.g., gateway server 390 which translates the INVITE message toa RAN-compliant call request signaling. The call may then be setup viaRAN 310 accordingly.

In accordance with an embodiment, a network of femtocell systems may bedeployed and connected with an IP backhaul. In this implementation, anauthorized UE may be serviced by the femtocell network, and service maybe transferred from one femtocell to another femtocell via a femtocellhandoff procedure. In the event that the femtocell network is deployedin an area serviced by a macrocellular network, handoff routines mayprovide preference for transferring a UE to a target femtocell systemrather than a macrocell site. In the event that a suitable femtocell isunavailable for handoff of a UE, the UE may be transferred to themacrocell site.

FIG. 6 is a diagrammatic representation of a network system 600featuring a femtocell network implemented in accordance with anembodiment of the invention. System 600 includes a RAN 610 that providesan over-the-air interface with a UE 625, e.g., a mobile terminal. RAN610 may comprise, for example, a CDMA radio access network or anothersuitable RAN. RAN 610 may comprise various BTSs 612 a-612 c andassociated BSCs 604 as well as other infrastructure as is understood.Each of BTSs 612 a-612 c provide a respective macrocell 602 a-602 c thatmay provide telecommunication service to UE 625. BSC 604 is coupled witha MSC 606 that provides cellular exchange services, mobility management,and other services within the area that it serves as is understood.

RAN 610 may interface with IMS 620 adapted to provide IP service to UE625. To this end, RAN 610 may be communicatively coupled with a SGSN 614and a GGSN 616. GGSN 616 is communicatively coupled with a PDF 618 thatprovides authorization of media plane resources. PDF 618 may becommunicatively coupled with a CSCF 620.

CSCF 620 comprises various SIP servers or proxies that process SIPsignaling packets in IMS 620. CSCF 620 may include a P-CSCF, a S-CSCF,and an I-CSCF as is understood. HSS 640 stores user profiles thatspecify subscription-related information of authorized users,authenticates and authorizes users, and provides information about theuser's physical location. Various application servers 642 a-642 n mayhost and execute services and is interfaced with CSCF 620 via SIP.

CSCF 620 is coupled with a BGCF 622 that comprises a SIP server thatprovides routing functionality based on telephone numbers. A MGCF 624performs call control protocol conversion between SIP and ISDN User Part(ISUP) and interfaces with a SGW 626 that itself interfaces with thesignaling plane of a circuit switched network, e.g., PSTN 630. A MGW 628interfaces with the media plane of PSTN 630 or another circuit switchednetwork. Resources of MGW 628 are controlled by MGCF 624. Fixed accessdevices, e.g., IP telephony devices 674 a-674 b, may connect with IMSnetwork via Internet 670 that is communicatively coupled with IMSnetwork 620 by way of border gateway 660.

Femtocell systems 650 a-650 c may include integrated BTS and BSC, oralternatively (or additionally) radio node (RN) and radio networkcontroller (RNC), functions and may feature additional capabilitiesavailable in the provided femtocell site coverage areas. Femtocellsystems 650 a-650 c provide an IP-accessible radio access network, areadapted for operation with IMS 620, and provide radio link controlfunctions. Femtocell systems 650 a-650 c may be communicatively coupledwith Internet 670 via any variety of backhaul technologies, such as an802.11x link, a 10/100 BaseT LAN link, a T1/E1 Span or fiber, cable settop box, DSL modem connected with a central office digital subscriberline access multiplexer, a very small aperture terminal (VSAT), oranother suitable backhaul infrastructure. In the illustrative example,femtocell systems 650 a-650 c are each coupled with an IP backhaulaccess device 655, such as an Ethernet cable or DSL router. Forinstance, femtocell systems 650 a-650 c may be coupled with access node655 via respective 10/100BaseT twisted pair cables, Category 5 cabling,or other suitable interconnection.

Each of femtocell systems 650 a-650 c provide a respective femtocellsite 651 a-651 c in which UE 625 may be provided telecommunicationservices over an air interface. Femtocell systems 650 a-650 c arecommunicatively coupled with one another via access device 655.Femtocells 650 a-650 c deployed for conjunctively providing a femtocellservice coverage area comprised of the collective femtocell sites 651a-651 c are collectively referred to herein as a femtocell network. Inan embodiment, femtocell systems 650 a-650 c may exchange messages withone another to facilitate handoff of a UE from one femtocell to another,e.g., as UE 625 moves out of the radio range of a femtocell and into theradio range of another. In the depicted example, the femtocell networkprovided by femtocell systems 650 a-650 c is at least partiallyoverlapped by one or more macrocell sites 602 a-602 c provisioned bymacrocell BTSs 612 a-612 c. In such an implementation, femtocell systems650 a-650 c may provide preference to another femtocell for handoff of aUE thereto. In the event that another femtocell is not available or isunsuitable for a handoff, the UE may then be transferred tomacrocellular coverage via a handoff to a macrocell BTS.

In an embodiment, each of femtocell system 650 a-650 c include arespective SIP adapter that supports a SIP client pool and providesconversion of call set-up functions to SIP client set-up functions.Additionally, femtocell systems 650 a-650 c include ESN screening toallow only designated UEs to access the femtocells thereby restrictingaccess to authorized home or small office UEs. Provisioning of ESN(s)may be made as part of an initial femtocell system activation. In theillustrative example, femtocell systems 650 a-650 c are allocated arespective IP address of “66.249.73.42”, “66.249.73.43”, and“66.249.73.44”, and UE 625 is allocated a MSISDN number, or E.164number, of “12145551212”.

FIG. 7 is a diagrammatic representation of an exemplary softwareconfiguration 700 of a UE, such as UE 625, adapted for engaging incommunications with femtocell systems in accordance with an embodiment.In the exemplary configuration of FIG. 7, the UE is configured withaccess network-specific software entities 760, e.g., protocol and driversoftware associated with a particular access network technology, such asCDMA, GSM, UMTS, or another suitable radio access network, and isdependent on the particular cellular and femtocell access technology inwhich the UE is to be deployed. While configuration 700 depicts a UEadapted for deployment in a single access network technology type, theUE may be implemented as a multi-mode device and may accordingly includea plurality of access-specific entities in accordance with anembodiment. The particular configuration 700 is illustrative only and isprovided only to facilitate an understanding of embodiments disclosedherein.

In the illustrative example, configuration 700 includes a cellular modemdriver 702 for providing a physical interface with the access network inwhich the UE is deployed. An access-stratum 704 and a non-access stratum706 may be included in configuration 700. A cellular radio interface 708may be communicatively coupled with lower layers of configuration 700and may additionally interface with network and session managementlayers, e.g., a network stack 710. Configuration 700 may include anoperating system 714, such as Symbian, Blackberry O/S, or anotheroperating system suitable for mobile applications, and may coordinateand provide control of various components within the UE.

Configuration 700 may include a femto application 712 that facilitatesfemtocell network acquisition and handoff of a UE from a macrocellularnetwork to a femtocell system in accordance with an embodiment. In oneimplementation, a femtocell or femtocell network, such as thatcomprising femtocell systems 650 a-650 c, may be acquired by amicro-pilot assisted handoff routine or a mobile assisted handoffroutine as described more fully hereinbelow. Configuration 700 mayinclude a preferred roaming list (PRL) 716 that contains informationused during the system selection and acquisition process. PRL 716indicates which bands, sub-bands and service provider identifiers willbe scanned, and the priority of the scan order. In the illustrativeexample, PRL 716 includes four entries 716 a-716 d that respectivelyspecify four networks (illustratively designated “Femto”, “Macro 1”,“Macro 2”, and “Roam 1”). In the present example, assume “Femto” refersto the network of femtocell systems 650 a-650 c. The femtocell networkis specified first in the prioritized list of PRL entries and thusindicates that the femtocell network is the preferred access network.Assume “Macro 1” refers to radio access network 610, and “Macro 2”refers to another cellular network. “Roam 1” specified by PRL entry 716d may refer to another cellular network that may have a roamingagreement with the UE home network. As is understood, PRL 716 maycomprise an acquisition table that specifies a list of frequenciesassociated with each of the networks specified in the roaming list onwhich the UE may scan during search of a particular system and mayfurther specify PN offsets thereof. The acquisition table mayadditionally specify a network type of each listed network andassociated channel blocks. Optionally, the configuration 700 may includea preferred user zone list (PUZL) 718. As is understood, the UE may usethe PUZL 718 to locate and use preferred access points. The PUZL 718provides priority and characteristics of the access points available tothe UE. When, for example, a neighbor list is provided to the UE, the UEmay compare access points of the neighbor list to the access points inthe PUZL 718. If a match is found, the UE may then attempt to locate theaccess point.

In accordance with an embodiment, a micro-pilot assisted handoff routinemay be implemented to facilitate handoff of a UE from a macrocellularsystem to a femtocell system. In this embodiment, a femtocell system, oran adjunct device, may transmit very low power pilot, paging, and synch(PPS) channels. Transmission of the PPS may be made on a commonfrequency used by the macrocellular system for macrocellular PPStransmissions. To this end, transmission of the PPS may be made at apower level for a short range transmission distance, e.g., 30 feet,thereby ensuring capture of the PPS by a UE proximate the femtocellsystem while otherwise providing low interference to other UEs withinthe macrocellular system. The PPS may include a unique systemidentification number (SID)/network identification number (NID) assignedto the femtocell system and may be implemented with a hoppingmicro-pilot to facilitate additional macro carriers. In otherimplementations, another unique identifier may be assigned to thefemtocell system in lieu of a SID/NID. Reference to a SID/NID assignedto a femtocell system is exemplary only, and another identifier may besuitably substituted therefor. In another implementation, the femtocellsystem PPS may be transmitted on a different carrier than that used bythe macrocellular system.

In an embodiment, numerous femtocell systems may use a common PN offsetshared among the femtocell systems. Thus, detection of the PPS with thePN provides an indication that the UE is within range of a femtocellsystem. The UE may then compare the SID/NID with a SID/NID included inPRL 716 to determine if the UE is authorized to access the femtocellsystem. If so, the UE may then attempt to register with the femtocellsystem for transfer of communication services from the macrocellularsystem to the femtocell system. In another implementation, a genericSID/NID may be assigned to a femtocell system, and the generic SID/NIDmay be used in conjunction with the micro-pilot to provide a viableconfiguration for a shared femtocell network access mechanism wherebyany user is permitted to access the femtocell system.

FIG. 8 is a flowchart 800 depicting a micro-pilot assisted handoffroutine that facilitates handoff of a user equipment from amacrocellular network to a femtocell system in accordance with anembodiment. The processing steps of FIG. 8 may be implemented on acomputer-readable medium as computer-executable instructions processedby a user equipment.

The handoff routine is invoked (step 802), and when the UE moves withinthe short range of a femtocell system transmitting PPS on the primarycarrier, F1, the UE observes the PPS (step 804). In another embodiment,the PPS may include a global service redirection message (GSRM) thatspecifies a particular femtocell carrier frequency. The femtocell systemmay be configured with a generic pseudo-noise (PN) offset that isincluded in the neighbor list of the macrocellular system. The UE thendecodes the SID/NID included in the PPS (step 806) and determineswhether the SID/NID of the PPS is a SID/NID assigned to a femtocellsystem (step 808). For example, the UE may compare the SID/NID with thehighest priority PRL entry to determine if the SID/NID matches theprioritized PRL entry, that is the femtocell system allocated thehighest priority in the PRL. If the SID/NID is not a femtocell systemSID/NID, the UE may remain on the macrocell carrier (step 810), and thehandoff routine cycle may end (step 818). If the SID/NID is evaluated asa femtocell system SID/NID at step 808, the UE may then switch to afemtocell carrier, F2, and attempt to register with the femtocell system(step 812). In an alternative embodiment, the macrocellular system andfemtocell system may share a common carrier. In another embodiment, thePPS may include a GSRM as noted above. In this instance, the UE mayswitch to the carrier specified in the GSRM at step 812. The femtocellcarrier, F2, may be read by the UE from PRL entry 716 a. Theregistration attempt by the UE may include transmission of the UE's ESN.The femtocell system may, in turn, compare the ESN received from the UEwith one or more ESNs configured in the femtocell system of UEsauthorized to access the femtocell system. If the ESN is an authorizedESN, the femtocell system may complete registration of the UE and notifythe UE accordingly. If the ESN is not an authorized ESN, the femtocellsystem may transmit a registration failure notification to the UE. Anevaluation may then be made by the UE to determine if the femtocellsystem successfully validated the UE's ESN and accepted the UEregistration (step 814). If the ESN is not accepted by the femtocellsystem, the UE may return to the macrocellular carrier, F1, according tostep 810. If the ESN is accepted by the femtocell system, registrationof the UE with the femtocell system may then be completed and the UE mayremain on the femtocell (step 816). The handoff routine cycle may thenend according to step 818.

In accordance with another embodiment, a mobile assisted handoff routinefacilitates handoff of a UE from a macrocellular system to a femtocellsystem. In this implementation, PRL 716 may be provisioned eithermanually or over-the-air. PRL entry 716 a for the femtocell system mayinclude a unique SID/NID and PN for one or more femtocell systems withwhich the UE is authorized to access. The UE may be configured toperiodically enter a search mode to attempt to locate the femtocellsystem. In an embodiment, the NID may comprise an extended NID toaccommodate more unique network IDs. In operation, the UE may beregistered on the macrocellular network on a macro carrier, F1.Periodically, the UE may switch to a femto carrier, F2, that isspecified in PRL entry 716 a allocated for the femtocell system and lookfor the femtocell PN specified in PRL entry 716 a. If the PN is located,the UE may then decode the SID/NID and determine whether the SID/NIDmatches the SID/NID of the home femtocell system. If the SID/NIDmatches, the UE may then register on the femtocell system. Otherwise,the UE returns to the macrocellular carrier F1.

FIG. 9 is a flowchart 900 depicting a mobile assisted handoff routinethat facilitates handoff of a user equipment from a macrocellularnetwork to a femtocell system in accordance with an embodiment. Theprocessing steps of FIG. 9 may be implemented on a computer-readablemedium as computer-executable instructions processed by a userequipment.

The UE may be provisioned with a PRL 716, e.g., either manually orover-the-air. In an embodiment, the PRL includes a unique SID/NID and PNallocated for one or more femtocell systems with which the UE isauthorized to access. The UE may be registered with a macrocellularsystem. The mobile assisted handoff routine is invoked (step 902). TheUE may be configured to periodically, e.g., at a pre-defined interval,invoke a femto search mode to look for the home femtocell system(s) byswitching to a common femto-channel, F2, as configured in PRL 716 (step904). An evaluation may then be made by the UE to determine if the femtoPN if found on the femto channel (step 906). If the femto PN is notfound on the channel, the UE may then return to the macro cell channel,F1, to continue with service provided by the macrocellular system (step908), and the mobile assisted handoff routine cycle may then end (step916).

Returning again to step 906, if the femto PN is detected on thefemto-channel, the UE may then decode the SID/NID (step 910) andevaluate whether the SID/NID belongs to the UE's home femtocell system(step 912). If the SID/NID does not belong to the home femtocell system,the UE may return to the macrocellular channel according to step 908. Ifit is determined that the SID/NID belongs to the UE's home femtocellsystem, the UE may then register with the femtocell system (step 914),and may then engage in communication services therewith. The mobileassisted handoff routine cycle may then end according to step 916.

As described, a communication system featuring an IP-based femtocellsystem for provisioning communication services to a user equipment isprovided. In one implementation, a micro-pilot assisted handoff routinemay be implemented to facilitate handoff of a UE from a macrocellularsystem to a femtocell system. In this embodiment, a femtocell system oran adjunct thereto may transmit very low power pilot, paging, and synchchannels on a common frequency used by the macrocellular system. The PPSmay include a unique SID/NID or other identifier assigned to thefemtocell system. The PPS may also include a global service redirectionmessage to direct the UE to a specific femto channel and/or SID/NID.Detection of the PPS with a PN allocated for femtocell systems providesan indication that the UE is within range of a femtocell system. The UEmay then compare the SID/NID with a SID/NID included in the UE'spreferred roaming list to determine if the UE is authorized to accessthe femtocell system. If so, the UE may then attempt to register withthe femtocell system. In another embodiment, a mobile assisted handoffroutine facilitates handoff of a UE from a macrocellular system to afemtocell system. In this implementation, the UE's PRL may beprovisioned either manually or over-the-air. A PRL entry for thefemtocell system may include a unique SID/NID and pseudo-noise offsetfor one or more femtocell systems with which the UE is authorized toaccess. The UE may be configured to periodically enter a search mode toattempt to locate the femtocell system by switching to a femto carrierthat is specified in a preferred roaming list entry allocated for thefemtocell system and look for the femtocell pseudo-noise offsetspecified in the preferred roaming list entry. If the pseudo-noiseoffset is located, the UE may then decode the SID/NID and determinewhether the SID/NID matches the SID/NID of the home femtocell system. Ifthe SID/NID matches, the UE may then register on the femtocell system.

The flowcharts of FIGS. 8-9 depict process serialization to facilitatean understanding of disclosed embodiments and are not necessarilyindicative of the serialization of the operations being performed. Invarious embodiments, the processing steps described in FIGS. 8-9 may beperformed in varying order, and one or more depicted steps may beperformed in parallel with other steps. Additionally, execution of someprocessing steps of FIGS. 8-9 may be excluded without departing fromembodiments disclosed herein.

The illustrative block diagrams depict process steps or blocks that mayrepresent modules, segments, or portions of code that include one ormore executable instructions for implementing specific logical functionsor steps in the process. Although the particular examples illustratespecific process steps or procedures, many alternative implementationsare possible and may be made by simple design choice. Some process stepsmay be executed in different order from the specific description hereinbased on, for example, considerations of function, purpose, conformanceto standard, legacy structure, user interface design, and the like.

Aspects of the present invention may be implemented in software,hardware, firmware, or a combination thereof. The various elements ofthe system, either individually or in combination, may be implemented asa computer program product tangibly embodied in a machine-readablestorage device for execution by a processing unit. Various steps ofembodiments of the invention may be performed by a computer processorexecuting a program tangibly embodied on a computer-readable medium toperform functions by operating on input and generating output. Thecomputer-readable medium may be, for example, a memory, a transportablemedium such as a compact disk, a floppy disk, or a diskette, such that acomputer program embodying the aspects of the present invention can beloaded onto a computer. The computer program is not limited to anyparticular embodiment, and may, for example, be implemented in anoperating system, application program, foreground or background process,driver, network stack, or any combination thereof, executing on a singleprocessor or multiple processors. Additionally, various steps ofembodiments of the invention may provide one or more data structuresgenerated, produced, received, or otherwise implemented on acomputer-readable medium, such as a memory.

Although embodiments of the present invention have been illustrated inthe accompanied drawings and described in the foregoing description, itwill be understood that the invention is not limited to the embodimentsdisclosed, but is capable of numerous rearrangements, modifications, andsubstitutions without departing from the spirit of the invention as setforth and defined by the following claims. For example, the capabilitiesof the invention can be performed fully and/or partially by one or moreof the blocks, modules, processors or memories. Also, these capabilitiesmay be performed in the current manner or in a distributed manner andon, or via, any device able to provide and/or receive information.Further, although depicted in a particular manner, various modules orblocks may be repositioned without departing from the scope of thecurrent invention. Still further, although depicted in a particularmanner, a greater or lesser number of modules and connections can beutilized with the present invention in order to accomplish the presentinvention, to provide additional known features to the presentinvention, and/or to make the present invention more efficient. Also,the information sent between various modules can be sent between themodules via at least one of a data network, the Internet, an InternetProtocol network, a wireless source, and a wired source and viaplurality of protocols.

What is claimed is:
 1. A method of handoff of a user equipment from amacrocellular system to a femtocell system, comprising: provisioning theuser equipment with a preferred roaming list that includes an entryallocated for the femtocell system that specifies a systemidentification number and network identification number associated withthe femtocell system, the system identification number and networkidentification number being transmitted by the femtocell on a secondcarrier frequency that is different than a first carrier frequency usedby the macrocellular system; wherein the preferred roaming listspecifies the second carrier frequency as associated with the femtocellsystem; detecting, by the user equipment, the system identificationnumber and network identification number over an air interface;evaluating the preferred roaming list to determine whether the detectedsystem identification number and network identification number match thesystem identification number and the network identification numberassociated with the femtocell system; reading a pseudo-noise offsetassociated with the femtocell system from the preferred roaming list,wherein detecting the system identification number and networkidentification number comprises switching, at a predefined interval,from the first carrier frequency to the second carrier frequency toattempt detection of the system identification number and the networkidentification number and detecting the system identification number andnetwork identification number at the pseudo-noise offset; decoding, bythe user equipment, the system identification number and the networkidentification number and determining whether the system identificationnumber and the network identification number is assigned to thefemtocell system; comparing, by the user equipment, the systemidentification number and the network identification number with thepreferred roaming list entry to determine if the system identificationnumber and the network identification number match the preferred roaminglist entry; and when the system identification number and the networkidentification number match the preferred roaming list entry,registering the user equipment with the femtocell system; andidentifying a service provider prioritized list from the preferredroaming list.
 2. The method of claim 1, wherein detecting the systemidentification number and network identification number comprisesdetecting a pilot, paging, and sync channel that includes the systemidentification number and network identification number.
 3. The methodof claim 2, wherein the pilot, paging, and synch channel is transmitted,by the femtocell system, on a common carrier frequency used by themacrocellular system.
 4. The method of claim 2, wherein the pilot,paging, and synch channel is transmitted, by the femtocell system, onthe second carrier frequency.
 5. The method of claim 1, furthercomprising allocating an entry for the femtocell system in the preferredroaming list, where the entry is allocated as a preferred network. 6.The method of claim 1, wherein evaluating the preferred roaming listresults in determining the detected system identification number andnetwork identification number match the system identification number andthe network identification number associated with the femtocell system,the method further comprising registering with the femtocell system. 7.A non-transitory computer-readable medium having computer-executableinstructions for execution by a processing system, thecomputer-executable instructions for facilitating handoff of a userequipment from a macrocellular system to a femtocell system, thecomputer-readable medium comprising instructions for: provisioning theuser equipment with a preferred roaming list that includes an entryallocated for the femtocell system that specifies a systemidentification number and network identification number associated withthe femtocell system, the system identification number and networkidentification number being transmitted by the femtocell on a secondcarrier frequency that is different than a first carrier frequency usedby the macrocellular system; wherein the preferred roaming listspecifies the second carrier frequency as associated with the femtocellsystem; reading a pseudo-noise offset associated with the femtocellsystem from the preferred roaming list; detecting, by the userequipment, the system identification number and network identificationnumber over an air interface at the pseudo-noise offset evaluating thepreferred roaming list to determine whether the detected systemidentification number and network identification number match the systemidentification number and the network identification number associatedwith the femtocell system; reading a pseudo-noise offset associated withthe femtocell system from the preferred roaming list, wherein detectingthe system identification number and network identification numbercomprises switching, at a predefined interval, from the first carrierfrequency to the second carrier frequency to attempt detection of thesystem identification number and the network identification number anddetecting the system identification number and network identificationnumber at the pseudo-noise offset; when the system identification numberand the network identification number match the preferred roaming listentry, registering the user equipment with the femtocell system; andidentifying a service provider prioritized list from the preferredroaming list.
 8. The non-transitory computer-readable medium of claim 7,wherein the instructions for detecting the system identification numberand network identification number comprise instructions for detecting apilot, paging, and sync channel that includes the system identificationnumber and network identification number.
 9. The non-transitorycomputer-readable medium of claim 8, wherein the pilot, paging, andsynch channel is transmitted, by the femtocell system, on a commoncarrier frequency used by the macrocellular system.
 10. Thenon-transitory computer-readable medium of claim 8, wherein the pilot,paging, and synch channel is transmitted, by the femtocell system, onthe second carrier frequency.
 11. The non-transitory computer-readablemedium of claim 7, further comprising instructions for allocating anentry for the femtocell system in the preferred roaming list, where theentry is allocated as a preferred network.
 12. The non-transitorycomputer-readable medium of claim 7, wherein the instructions forevaluating the preferred roaming list determine the detected systemidentification number and network identification number match the systemidentification number and the network identification number associatedwith the femtocell system, the computer-readable medium furthercomprising instructions for registering the user equipment with thefemtocell system.
 13. A system configured for macrocellular to femtocellsystem handoff, comprising: a packet-switched network; an InternetProtocol multimedia subsystem communicatively interfaced with thepacket-switched network; a macrocellular system with which a userequipment has authorized access; and a femtocell system communicativelycoupled with the packet-switched network adapted to provide a radiointerface with the user equipment, wherein the femtocell system isconfigured with an electronic serial number of the user equipment and isconfigured to transmit the system identification number and networkidentification number on a second carrier frequency that is differentthan a first carrier frequency used by the macrocellular system, whereinthe preferred roaming list specifies the second carrier frequency asassociated with the femtocell system, wherein the user equipment isprovisioned with a preferred roaming list that includes an entryallocated for the femtocell system that specifies a systemidentification number and network identification number associated withthe femtocell system, wherein the user equipment is configured toswitch, at a predefined interval, from the first carrier frequency tothe second carrier frequency to attempt detection of the systemidentification number and the network identification number, when thesystem identification number and the network identification number matchthe preferred roaming list entry, register the user equipment with thefemtocell system; wherein the femtocell system transmits the systemidentification number and network identification number that is detectedby the user equipment, and wherein the user equipment evaluates thepreferred roaming list to determine whether the detected systemidentification number and network identification number match the systemidentification number and the network identification number associatedwith the femtocell system, and wherein the user equipment identifies aservice provider prioritized list from the preferred roaming list,wherein the user equipment reads a pseudo-noise offset associated withthe femtocell system from the preferred roaming list, and wherein theuser equipment detects the system identification number and networkidentification number at the pseudo-noise offset.
 14. The system ofclaim 13, wherein the user equipment determines the detected systemidentification number and network identification number matches thesystem identification number and network identification numberassociated with the femtocell system and attempts to register with thefemtocell system, and wherein the femtocell system completesregistration of the user equipment by verifying an electronic serialnumber of the user equipment matches the electronic serial numberconfigured in the femtocell system.